Project on Logic gates

Discussion in 'The Projects Forum' started by abhinavhardikar, Aug 3, 2010.

  1. abhinavhardikar

    Thread Starter New Member

    Aug 3, 2010
    3
    0
    I am doing a project on Logic gates! I have to verify the truth table of all the logic gates! so I started with OR gate. I bought IC 7432. But it isn't going well! It is functioning like this:

    inp1| inp2 |out
    0 | 0 |1

    Vcc=6V

    http://img195.imageshack.us/img195/7177/probpg.jpg

    can you please help me!!

    Thank you

    Abhinav
     
  2. erich_7719

    Active Member

    Oct 14, 2009
    92
    7
    Tie all you inputs to ground and see what you get.
     
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  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    If you look at the spec sheet, you will notice that the maximum for Vcc for a TTL IC is 5.5 volts. The usual range is 4.5 - 5.0 volts. Applying 6 volts to pin 14 may have damaged the IC.

    Your photo is too dark to make out the location of pin 1. Hopefully you have put ground and Vcc to the proper pins.

    One further problem are the 6 inputs not connected. TTL IC's do not like this. The input voltage tends to rise to the operating point and cause oscillations. The result is a hot IC which is prone to malfunction. You should connect thise input pins to ground - the outputs may be left open.
     
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  4. abhinavhardikar

    Thread Starter New Member

    Aug 3, 2010
    3
    0
    I don't get an output!! It works!! Let me try it with AND gate
     
  5. abhinavhardikar

    Thread Starter New Member

    Aug 3, 2010
    3
    0
    thank you very much! the PD is approx 5V because of high internal resistance! I checked it with a multimeter! Could someone tell me where I can find the internal circuit of the ICs?
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Use the logic gate number as a search term. You will find many links to data sheets.
     
  7. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    Assuming pin 1 is the closest we see in your picture.

    You have gate 4's inputs floating. They can be low or high ... not floating. The same applies to any unused gates as well.

    Your LED needs 150 ohm resistor to limit drop the difference between the output voltage, when it's high, and the 1.5V needed by the LED. A 150 ohm will suffice.

    on edit ...

    here is the schematic of one 7432 Or gate ... from the datasheet
     
    Last edited: Aug 3, 2010
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